1. Field of the Invention
The present invention pertains to pollution prevention devices and, more particularly, to an assembly for use during the filling of liquid storage vessels to capture spilled liquids.
2. Description of the Prior Art
Much of the earlier prior art relating to liquid storage tanks dealt with atmospheric pollution and tank venting systems. These were used to prevent excessive pressure build-up while preventing escape of pollutant vapors. Subsequently, concern arose regarding contamination of the soil. Toxic materials in the soil were found to create long-lasting hazardous conditions. Seepage of toxic liquids into ground water supplies affect not only drinking water, but crops which are consumned by animals and humans. Also, flammable liquids have been known to seep into basements and drainage systems creating explosive havoc.
One area of concern has been the prevention of spills about liquid storage tanks. Tanks that are repetitively depleted and refilled with toxic and/or flamable liquids are especially prone to spillage of pollutant chemicals. Most notable are the tanks used in the chemical industry to house reactants, solvents, by-products and finished materials. Also of note are the underground fuel tanks commonly found in service stations. In the above situations, spillage often occurs through tank overfilling, weak line connections, drainage from disconnected lines, faulty gaskets, leaky valve seals and the like.
Attempts to contain spillage from the above exemplary situations are described in U.S. Pat. Nos. 4,278,115; 4,501,305 and 4,520,852. U.S. Pat. No. 4,278,115 describes the construction of a manhole about the fill pipe of a storage vessel. The manhole bottom slopes toward a valved drain outlet leading to an auxiliary holding tank. Spilled liquids are received in the manhole and drained to the holding tank where they are accumulated for later removal.
A problem with the above device is that it is wholly dependent on the effectiveness of a seal about the manhole bottom and storage vessel fill pipe. Such a seal is necessary to accomodate axial movement of the fill pipe relative to the manhole bottom caused by natural forces such as earth movement, tank settling and pipe contraction and expansion resulting from ambient temperature variations. Unless the seal maintains its effectiveness during such movement, the spillage will leak directly into the soil beneath the manhole bottom.
Also, the addition of a separate holding tank and accompanying pipe, fittings and seals multiplies potential leakage sources. Still further, it creates substantial additional capital investment costs, installation costs and maintenance costs.
Another disadvantage is that the extra holding tank will require occasional pumping-out. Also, the connector piping and fitments must, in some manner, accommodate movement caused by the above-described natural forces. Clearly, all of the above add to the cost and unreliability of the auxiliary tank system.
U.S. Pat. Nos. 4,501,305 and 4,520,852 both disclose spill collectors that utilize polymer imbiber bends to selectively absorb organic fuels while allowing only water to pass into the surrounding earth. The obvious major disadvantage of the above concerns the need for frequent monitoring and replacement of the beads. In U.S. Pat. No. 4,501,305 this is especially important since the receptacle is open-ended. Once the beads have become saturated, additional spillage will flow directly into the soil.
Also, the device of U.S. Pat. No. 4,520,852 continues the aforementioned problem of the necessity for an effective sealing means between the storage tank fill pipe and the receptacle bottom. Constant monitoring and careful maintenance are required to insure that no leakage occurs.
In addition to the above, it should be noted that none of the aforereferenced prior art seek to fully prevent the entry of water into the receptacle. In fact, although covers are mentioned, the unsealed downwardly stepped rim designs of the cited art actually facilitate water flow about the cover periphery and into the spill receptacles. Obviously, this is detrimental since water is a contaminant for fuels and should be excluded whenever possible.